This invention relates generally to male pin electrical connectors, and specifically to such connectors adapted for use in oil well tools.
Once an oil well is drilled, it is common to log certain sections of the well with electrical instruments. These instruments are sometimes referred to as "wireline" instruments, as they communicate with the logging unit at the surface of the well through an electrical wire or cable with which they are deployed. In vertical wells, often the instruments are simply lowered down the well on the logging cable. In horizontal or highly deviated wells, however, gravity is frequently insufficient to move the instruments to the depths to be logged. In these situations, it is sometimes necessary to push the instruments along the well with drill pipe.
Wireline logging with drill pipe can be difficult, however, because of the presence of the cable. It is cumbersome and dangerous to pre-string the electrical cable through all of the drill pipe before lowering the instruments into the well. Some deployment systems have therefore been developed, such as Schlumberger's Tough Logging Conditions System (TLCS), that make the electrical connection between the instruments and the cable down hole, after the instruments have been lowered to depth. In these systems, the electrical instruments are easily deployed with standard drill pipe, and the cable is then run down the inside of the drill pipe and connected. After logging, the cable can be easily detached from the logging tool and removed before the tool is retrieved. The TLCS has been very effective and has achieved strong commercial acceptance.
In the TLCS and other systems, the cable is remotely connected to the instrumentation with a down hole connector. One half portion of this connector is attached to the instrumentation and lowered into the well on drill pipe. The other half portion of the connector is attached to the end of the cable and pumped down the drill pipe with a flow of mud that circulates out of open holes at the bottom of the drill pipe and into the well bore. The connector is sometimes referred to as a "wet connector" because the connection is made in the flow of drilling mud under conditions that challenge electrical connection reliability.
Internal connectors used in such well tools, such as for connecting internal leads from the tool to the wet connector, also have to withstand difficult field conditions. The best of tool sealing techniques can, on occasion, fail to keep electrically conductive well fluids from infiltrating the internal connection area. In some applications, extreme pressure differentials (sometimes up to 15,000 psi, for instance) across connectors can tend to force fluids to migrate along interfaces between various connector components or even inside conductor insulation. Down hole temperatures can also reach extreme levels, excluding the use of common seal and connector materials of some commercial connectors. Internal connectors must therefore be tightly sealed and properly constructed to protect against both known and unforeseen down hole environments and circumstances.
Furthermore, down hole tools must be designed to fit down small diameter wells, sometimes as small as four inches in diameter or less. This size constraint is passed along to the internal connectors, which sometimes are forced to fit within bores of only one-inch diameter or less. Within this package size the internal connector must provide, depending upon the application, individually isolated connection for up to eight or more electrical conductors to provide power and signal connection from the tool to the surface of the well. Because typically such connectors are mounted within load-carrying members (which are therefore desirably made of steel or other metal), the possibility exists for shorting between closely-spaced connector pins and such nearby metal surfaces.
Such internal connectors must also be easy to assemble, sometimes in the field if troubleshooting or repair are required. Also, quick pin-out reconfiguration of multi-pin connectors is desirable for overcoming unforeseen field problems, such as an internal break in a conductor within the cable. To meet these requirements, it is necessary that the separate wires from the tool be individually connectable to the internal connector. This individual connection requirement precludes the use of a unitary female multi-pin connector. Instead, such down hole tools are generally constructed with individual female pin sockets on each tool wire for connection with a pin of the internal connector. Such construction, while enabling easy assembly and reconfiguration, provides additional challenges of sealing and shorting resistance that are more conveniently addressed in typical unitary female pin connectors.